Various types of turbo-machinery, such as gas turbine engines, are known and widely used for power generation, propulsion, and the like. The efficiency of the turbo-machinery depends in part upon the clearances between the internal components and the leakage of primary and secondary fluids through these clearances. For example, large clearances may be intentionally allowed at certain rotor-stator interfaces to accommodate large, thermally-induced, relative motions. Leakage of fluid through these gaps from regions of high pressure to regions of low pressure may result in poor efficiency for the turbo-machinery. Such leakage may impact efficiency in that the leaked fluids fail to perform useful work.
Different types of sealing systems thus are used to minimize the leakage of fluid flowing through turbo-machinery. The sealing systems, however, often are subject to relatively high temperatures, thermal gradients, and thermal expansion and contraction during various operational stages that may increase or decrease the clearance therethrough. For example, interstage seals on gas turbines and the like may be limited in their performance as the clearances change from start-up to steady state operating conditions. Typical sealing systems applied to such locations include labyrinth seals and brush seals. In the case of labyrinth seals, clearances may be set with a predetermined increased margin so as to avoid contact therewith. This extra clearance, which is useful during the start-up phase of operation, may reduce the efficiency and performance of the turbo-machinery as the leakage increases across the seal during the steady-state phase of operation. Moreover, such labyrinth seals typically are intolerant of changes in the radial clearance of the rotating shaft.
There is thus a desire for improved sealing assemblies and systems for use with turbo-machinery. Preferably such sealing assemblies and systems may provide tighter sealing during steady state operations while avoiding rubbing, wear caused by contact, and damage during transient operations. Such sealing assemblies and systems should improve overall system efficiency while being inexpensive to fabricate and providing a long lifetime.